Device for the maintenance of semi-autogenous grinding mills used in large-scale mining

ABSTRACT

A nut cold cutter devise is used in the assembly and maintenance of semi-autogenous grinding mills for large-scale mining. The device includes a front body, a back body and a hydraulic cylindrical chamber located between the front and back bodies. The front body has a defined cavity in which there is a movable cutting tool and a fixed cutting tool. The nut to-be-cut is positioned in the space located between the two cutting tools.  
     The hydraulic cylindrical chamber contains a push piston that is sealed to the inside of said hydraulic cylindrical chamber with watertight joints. The push piston is attached to a toolholder axis and the movable cutting tool is attached to the front end of the toolholder axis.

DESCRIPTION

[0001] This invention is aimed at creating a device for the maintenanceof semi-autogenous grinding mills used in large-scale mining. Inspecific terms, the invention entails a hydraulically powered, nut coldcutting device with a movable cutting tool and a fixed cutting tool.Furthermore, this tool can be interfaced with a guided or remote controlstation for easy operation.

1. PRIOR ART

[0002] As part of the large-scale copper mining explotation processes,grinding the rock containing the ore is a distinctively importantprocess along the chain of operations whose objective is to obtain highgrade metal. Said grinding is performed after the rock has beenextracted from the exploitation embankments and first crushed in theprimary, secondary and tertiary crushers, whichever may be the case.

[0003] Currently, the rock is also ground in semi-autogenous grindingmills (SAG mills), which are very large machines whose size usuallyranges from 9.7 to 11 meters in diameter and 4.5 to 5.2 meters inlength. Furthermore, these mills have an inner lining, such as liftersor rock elevators that facilitate the rock grinding process, which iswhy they are called semi-autogenous grinders.

[0004] The inner linings of this type of mill are subjected to strongimpact and friction produced by the rock, which clearly over timeresults in the wear and tear of the linings and their eventualreplacement. Likewise, these linings are attached to the mill's mainstructure or shell with nuts, bolts and washers. The bolt goes throughthe mill (passing through the inside and coming out at the other end),and the washer and nut are placed on the protruding end of the boltthereby tightly squeezing the abovementioned linings.

[0005] It is important to point out that these nuts, bolts and washersare very large in size since they must pass through the main structure,which is made out of thick.

[0006] As a result, when the lining reaches the end of its service life,the nuts must be loosened in order to free the bolts squeezing thelinings in place. Loosening the nuts is not at all simple since, aspreviously explained, they are so tightly in place that it ispractically impossible to loosen them by merely turning them. Therefore,the easiest way to take off the nuts is breaking them by way of a commonprocess known as oxy-cutting or oxyacetylene, which consists of using aflame torch with an oxygen/carbon mixture that weakens the metal (nut)by melting it, and that way it can be cut and then the fragments of thenut are separated.

[0007] This nut-removal process is performed by specially trainedprofessionals and is considered a high-risk job, basically because theworkers must “climb” the main structure of the mill, given its size, andthen they must perform the oxy-cutting, which implies a great risk ofaccidents given the likelihood of one of the workers falling from thetall mills and working amongst iron structures, nuts and bolts. Also,oxy-cutting involves additional risks given the sparks and hightemperature at which it is performed.

[0008] Furthermore, the time involved in replacing the linings entailssignificant costs in the copper metal production since in order to carryout such an operation, the site must shut down, therefore automaticallydecreasing the quantity of ore processed and, consequently, less metalis produced. Therefore, creating a device that would allow fordecreasing the time the mills needs to be shut down for maintenancepurposes automatically translates into increased production, asignificant decrease in risks and lower risk-related costs.

2. ADVANTAGES OF THE INVENTION

[0009] Having read the pre-art description and the drawbacks involved inSAG mill maintenance, the advantages of this invention device can bedescribed as follows:

[0010] A significant reduction in mill maintenance time given theincreased speed

[0011] A notable reduction in the human risk factor since that use ofthe invention device prevents high altitude work.

[0012] Use of oxy-cutting or oxyacetylene is avoided along with thetoxic gases given off by these processes.

[0013] Large savings in production-related costs since operations areshut down for less time for maintenance purposes.

[0014] It is possible to interface the tool with a guided or remotecontrol station given the lightweight of its overall structure.

[0015] It is entirely made out of wear and tear components that can beeasily removed and replaced.

[0016] It is compact, solid and easy to assemble.

3. BRIEF DESCRIPTION OF FIGURES

[0017]FIG. 1: provides a side view of the invention device.

[0018]FIG. 2: provides an overhead view with a cutaway view of theinvention device.

[0019]FIG. 3: provides a profile cutaway view of the invention device.

[0020]FIG. 4: provides an angle and cutaway view of the inventiondevice.

[0021]FIG. 5: provides an angle view of the invention device

4. DESCRIPTION OF THE INVENTION

[0022] The invention device is primarily made up of a front body (7), ahydraulic cylindrical chamber (1) a back body (8), in which thehydraulic cylindrical chamber (1) is located between said front body (7)and said back body (8).

[0023] The hydraulic cylindrical chamber (1) consists of a push piston(12) on the inside that remains sealed inside said chamber (1), whichdefines the piston stroke (12), based on the action of the watertightjoints (14). Said piston (12) is joined to a toolholder axis (11)through joining elements (13). Also, the front end (4) of the toolholderaxis (11) is where the movable cutting tool (15) is tied to the joiningelement (13′).

[0024] This way, when hydraulic force is applied to the push piston(12), the push piston is activated and moves the toolholder axis (11),which then causes the movable cutting tool (15) to move. The movablecutting tool's (15) geometry has a unique trait that is its anglefinishing (α), preferably a sharp angle, that makes it possible togenerate all the pressure exerted by the push piston (12) on onespecific point.

[0025] Because of its unique geometry, the movable cutting tool (15) isthe first component to penetrate the metallic body (10) to-be-destroyed.As it continues to penetrate along the initial fissure made in themetallic body (10), caused by the first penetration of the movablecutting tool (15), the pressure of the hydraulic force transmitted bythe push piston (12), makes the initial cut expand.

[0026] On this same imaginary axis (A) that defines the system's centeror device's longitudinal axis, and therefore the longitudinal axis ofthe movable cutting tool (15), facing the first cutting tool is a secondcutting tool (3) the same as the first but that cannot move, in otherwords, it remains fixed at all times.

[0027] As pressure is exerted onto the system, the second cutting tool(3) begins to penetrate the opposite end of the end originallypenetrated by the movable cutting begins to split on both ends along thesame imaginary axis (A) until being completely destroyed, and split intotwo pieces, after which it is no longer tightly secured.

[0028] As illustrated in FIG. 2, the cutting tool (3) is fixed onto theupper end (20) in a cavity (21) defined on the inside of the front body(7). Furthermore, the figure also illustrates that said cavity (21) ofthe front body (7) is where the to-be-destroyed metallic body (10)should be located. Also, on the lower end of the place where the cuttingtool's blade (3) is located, there is a pushing element (5) designed toslightly move the cutting tool (3) when said tool has already reachedthe end of its useful life, and remove said tool which will be replacedby a new one.

[0029] Two moving bodies (2) capable of sliding and being pressed by theaction of the forward movement of the springs (6) located on the insideof each upper side of the front body (7) are available in order toachieve an exact position of the metallic body (10) to-be-destroyed, inwhich usually, but not preferably, there is a nut commonly in ahexagonal peripheral section.

[0030] As illustrated in FIG. 2, said movable bodies (2) make itpossible for both cutting tools to make the cut in the metallic body(10) on one imaginary axis (A) of reference. That is, a parallelismaction is produced in the cut.

[0031] The movable bodies (2) are mounted on fixed guides (22) on theupper inside face of the front body (7). These guides (22) are a kind ofrail that prevents the movable bodies (2) from moving in the wrongdirection along their defined longitudinal course.

[0032] As a result of the action of the movable bodies (2), the metallicbody (10), in this case a hexagonal peripheral section, remains set orfixed in such a way that the cut is made in the area where the materialis least thick, thereby enabling the cut to be made as quickly aspossible exerting the least amount of wear and tear on the cutting toolsand on the device in general.

[0033] Furthermore, the front body (7) and the back body (9) can beeasily removed.

[0034] A connection shank (18) is attached to the back body (9). Saidshank (18) has an orifice (19) by way of which you can interface theinvention device with a remote control system. There is also a hydraulicfluid access point (17) located on the side of the back body (9) throughwhich the hydraulic fluid reaches the hydraulic chamber (1), and beginsto generate pressure on the push piston (12). A coupling (8) has beenadded to the hydraulic fluid access (17) making it possible to join theline of a hydraulic force generation system to the invention device.Likewise, the hydraulic fluid exit point is located on the front body(7) allowing for said fluid to return to the cited generation system.Just like on the hydraulic fluid access (17), a coupling (8′) has beenplaced on the hydraulic fluid exit (16) to allow for connecting theinvention device to the hydraulic force generation system.

[0035] From another perspective, the movable cutting tool (15) and thefixed cutting tool (3) are manufactured from steel covered incarbide-tungsten or carbide-silicon, or any other alloy with anextremely hard surface.

[0036] The front body (7) and the back body (9) have each beenmanufactured from one forged body that is subsequently thermally treatedand mechanized. These bodies are made from high-strength forged steelthat consists of a chrome-nickel-molybdenum combination as the mainalloy elements. The fact that the front and back bodies have beenmanufactured from forged steel makes it possible for the inventiondevice to respond uniformly under such force when performing its varioustasks. The cylindrical chamber (1) is manufactured from stainless steel.

[0037] The movable bodies (2) are manufactured from specialhigh-strength steel with chrome-nickel type alloy elements. The springs(6) are manufactured from steel commonly called “sprung steel,” which issteel with high silicon content.

[0038] Finally, the joining elements (13) and (13′) are also made out ofhigh-strength steel with a chrome-nickel alloy; and the front and backbodies are attached to the hydraulic chamber (1) by way of high-strengthbolts (23) with unique elasticity characteristics.

1. A nut cold cutter device used in the assembly and maintenance ofsemi-autogenous grinding mills for large-scale mining CHARACTERIZEDbecause it consists of: a front body, a back body and a hydrauliccylindrical chamber located between the front and back bodies; and saidfront body has a defined cavity in which there is a movable cutting tooland a fixed cutting tool, and the nut to-be-cut will be positioned inthe space located between the two cutting tools.
 2. The nut-cuttingdevice described in claim 1 CHARACTERIZED because said hydrauliccylindrical chamber contains a push piston on the inside that is sealedto the inside of said hydraulic cylindrical chamber with some watertightjoints.
 3. The nut-cutting device in claims 1 and 2 CHARACTERIZEDbecause said push piston is attached to a toolholder axis by joiningelements, and said movable cutting tool is attached to the front end ofsaid toolholder axis.
 4. The nut-cutting device in claim 3 CHARACTERIZEDbecause the geometry of said movable cutting tool has a unique traitwhich is a sharp angle finishing.
 5. The nut-cutting device in claim 1CHARACTERIZED because said fixed cutting tool is located in afront-facing position with respect to said movable cutting tool on thesame level defined by the cutting device's longitudinal axis.
 6. Thenut-cutting device in claims 1 and 5 CHARACTERIZED because said fixedcutting tool is interfaced with the upper inside end of said front body.7. The nut-cutting device in claim 1 CHARACTERIZED by the installationof two front mobile bodies, the two front mobile bodies having thecapacity to slide and to be pressed one against the other due to thesprings located on the front part of the mobile bodies; the springsallowing the nut to be cut in an exact position.
 8. The nut-cuttingdevice in claim 7 CHARACTERIZED because said movable bodies are mountedon fixed guides located on the inside upper side of said front body andprevent said movable bodies from moving in the wrong direction alongtheir defined longitudinal course.
 9. The nut-cutting device in claim 1CHARACTERIZED because a connection shank with an orifice through whichthe nut-cutting device can be connected to a remote control system, isattached to said back body
 10. The nut-cutting device in claim 1CHARACTERIZED because on the side of said back and front bodies there isa hydraulic fluid access and a hydraulic fluid exit, respectively, forsaid hydraulic cylindrical chamber.
 11. The nut-cutting device in claim10 CHARACTERIZED because couplings that allow for connecting thenut-cutting device up to a hydraulic force generation system have beenplaced on said hydraulic fluid access and exit.
 12. The nut-cuttingdevice in claim 1 CHARACTERIZED because said movable and fixed cuttingtools are manufactured from steel covered in carbide-tungsten orcarbide-silicon.
 13. The nut-cutting device in claim 1 CHARACTERIZEDbecause each of the said front and back bodies are manufactured from onesingle forged body that is subsequently thermally treated andmechanized.
 14. The nut-cutting device in claim 13 CHARACTERIZED becausesaid forged body is made from high-strength forged steel with acombination of chrome-nickel-molybdenum as the main alloy elements. 15.The nut-cutting device in claim 1 CHARACTERIZED by the body of saidcircular hydraulic camera being made of stainless steel.
 16. The nutcutting device in claim 1 CHARACTERIZED because said movable bodies aremanufactured from high-strength steel with chrome-nickel type alloyelements and because said springs are manufactured from steel with ahigh silicon content.